Mmm yeah i think its easy for Wii to win this if it keeps up the good numbers, and especially since it also has japan working much more on its favor.
If anything your prediction of the Wii selling 70 million at around april is bolder. Will Q1 2010>Q1 2009 for the Wii? Well January and Feb in the states were record breaking for the Wii, and outdoing that will be tough but possible because mainly of Japan as i've stated before. However Q2 2010 will be way better than 2009 imo since the momentum is much stronger this time around. At the same time i expect 360 to fall further and further down until natal+pricecut comes along.